1. Field of the Invention
This invention relates to the field of lawnmowers. More specifically, the invention comprises a lawnmower blade assembly which can be attached to a conventional lawnmower shaft.
2. Description of the Related Art
The overall design of the gas-powered and electric-powered lawnmower cutting system has remained unchanged in recent decades. The overall design uses an electric or gas motor to turn a shaft which extends in the direction of the ground beneath the motor. The shaft extends through a hole into the blade housing where a blade is attached to the shaft. The motor drives the shaft causing angular rotation of the blade within the housing. Grass that extends above the height of the blade is cut and discharged from the housing.
Various lawnmower replacement blades are known in the art. The designs of the replacements blades vary significantly and have been the subject of many U.S. patents. Although great efforts have been made to improve the design of replacement lawnmower blades, these designs have their shortcomings.
As an example, most commercially available blades are ineffective at neatly cutting grass when the grass is wet, tall, or thick. The rotation of a conventional blade slows down under these conditions as the lawn provides greater resistance to cutting. This resistance can often escalate as the rotation of the cutting blade continues to slow until the blade eventually stops. The escalation of resistance occurs because, as the blade slows down, the force at which the cut grass is ejected decreases. This results in the accumulation of cut grass in the housing which increases the force required to turn the blade.
Even under ideal cutting conditions, conventional blades are ineffective at “cutting” the grass. As a conventional blade begins to dull, more grass is “torn” than “cut.” As the blade strikes the grass, some of the grass is pulled by the blade until it breaks. This “tearing” of the grass results in increased cellular damage to the grass. This often causes the tip of the blade of grass to appear brown. It has also been noted that the increased cellular damage causes the grass to grow more quickly which requires more frequent mowing.
In order to address these disadvantages, some have proposed mounting two or more cutting blades on a common hub. In such an embodiment, the resistance provided by the lawn is spread out across twice as many cutting blades. In addition, each blade cuts approximately half as much grass as in the standard single blade mower, thus slowing the blade wear. These multiple blade designs can be more effective at cutting grass when the grass is wet, tall, or thick.
There are also disadvantages associated with using a mounting hub, however. First, mounting hubs take up space on the blade mounting shaft. Some shafts may not be long enough to accommodate the combination of two cutting blades, a mounting hub, and clamping collar. Also, many prior art hub designs can lose clamping force over time, allowing the blades to tilt or otherwise come out of alignment. Hubbed designs also tend to result in a flywheel effect—owing to the increase in rotational mass—which can cause the blades to bend when the blades strike a rock, ant hill, or root.
Thus, it would be desirable to provide an improved lawn mower blade assembly capable of realizing the advantages of multiple blade designs while avoiding the disadvantages associated with the use of a mounting hub.